Most households include water heaters to supply hot water for bathing and washing purposes. Such water heaters are typically adjustable to provide hot water at the desired temperature. Hotter water is usually desired for washing than for bathing. Many automatic dish washers and clothes washers require water heated to a particular temperature for proper operation. Thus, the water temperature required for clothes or dish washing is usually the controlling factor in setting the water heater.
Adjustment of the water temperature as desired for bathing and the like is simply accomplished by the user at the sink, tub or shower. Some attention is required because, in some cases, it is possible to become scalded, particularly if the water heater is positioned nearby or the supply lines are insulated, and there has been little or no temperature loss in line from the water heater. This can result in burns from scalding hot water, which of course is a dangerous condition. Excessive splashing can also occur if the volumetric flow rates of the hot water and cold water are not adjusted properly. These have been long standing problems associated with the use of water heaters that provide hot water for both bathing and washing.
Various non-scalding water valves have been developed heretofore, however, there have been several drawbacks to these prior devices. For example, U.S. Pat. Nos. 1,479,545 to Johnson; 1,551,226 and 1,615,730 to Vallier; 2,180,790 to Brummett; and 4,089,347 to Christo are representative of the prior art. One drawback has been that the prior devices have tended to be relatively complicated and thus expensive. Another drawback has been that the prior water temperature control devices have been adapted primarily for controlling only the hot water, and not the cold water as well. It will be appreciated that an unexpected blast of cold water can be a shock which could in turn cause the user to slip and fall in the tub and shower.
Yet another drawback with the prior water temperature control devices has been their lack of convenient adjustability. For example, U.S. Pat. No. 4,387,880 to Saarisalo shows a single-grip mixing valve that provides adjustability of either hot or cold temperature limits, but requires disassembly for adjustment.
Heretofore there has not been available a water temperature control safety unit of inexpensive construction that delivers a substantially constant volume of water within a preselected temperature range whose upper and lower limits can readily be adjusted as desired.